Ordered a fuckload of 4mm magnets on ebay a week back, finally got them through the post.
As beautifully powerful as you'd expect, and only 1mm thick :3
I know, hardly the most thrilling thing to post.
And guess what? In case you've spent your life trapped in a well, I have photos of them so you know what they look like!
I am tempted to sell some off to people who could do with some.